"We have been continually lied to in order for them to continually expand," neighbor Barry Levinson said. "This is for them to undertake to destroy a neighborhood that pays taxes ... I don't think any growth on behalf of Silver Hill should ever happen."

At issue was the house at 225 Valley Road, a property adjacent to the facility that Silver Hill purchased in December 2012 for $2.4 million. The hospital plans to add three bedrooms to the house, for a capacity of eight patients and five staff members. Silver Hill is a renowned psychiatric hospital that covers 60 acres in the Silvermine part of New Canaan.

Levinson said as evidence of the plan for expansion, he was contacted once by the hospital about selling his own house. He wondered why the hospital would continue to purchase property if it did not have a plan for expansion.

Some of the 16 neighbors who came out to the meeting to voice their opposition asked that the P&Z understand that they did not sign up for a neighborhood where an institution would be devouring land.

"There is an expectation when you move in that expansion will be regulated," David Rucci of the New Canaan-based law firm Lampert, Toohey & Rucci, LLC, said, representing the neighboring Turner family. "It's not reasonable to expect a facility to creep up on you."

Silver Hill's attorney, Mike Sweeney of the Stamford-based law firm Sandak, Hennessey and Greco, said the hospital has no master plan including expansion and would offer P&Z a pledge that the hospital would not acquire any new property outside its current boundaries for the next three years.

The assurance was not convincing to skeptical neighbors, as a round of laughter erupted from the room following Sweeney's pronouncement of just three years.

"What we have is an insular application which complies with your regulations, it is not a Machiavellian land grab," Sweeney said once the laughter had died down.

Many members had complaints that the addition of the in-patient residence would increase traffic and people in the bucolic neighborhood. They also griped about the frequent emergency services visits to the area.

"In the past 10 years, there have been 1,388 police responses to incidents," Levinson said. "Ambulance paramedics had to arrive at Silver Hill 152 times in 2012."

The Silver Hill team refuted the lower property value argument by bringing in an appraiser, Michael Gold of Westport-based Michael Gold Associates.

"It's my opinion that the proposed change of use would have no measurable impact on neighborhood property values," he told the commission.

Sperry DeCew, a member Silver Hill's board of directors and a member of the New Canaan Police Commission, said Silver Hill has been a good neighbor and increased property values.

"Over the past 10 years Silver Hill has spent $15 million to renovate existing structures, with no expansion," he said. "There's a further plan to improve roadways and walkways at considerable cost which would have an enormously good impact on the community."

In closing the public hearing, Laszlo Papp, chairman of the P&Z, said the commission would debate the merits of the arguments at next month's meeting and decide either then or at the following one.

One question remaining was: What would happen to the building if the permit was denied? Silver Hill has already paid $2.4 million for it.

"I don't know," Sigurd Ackerman, president of Silver Hill said, after the meeting.